Very much heavier than the 6-Series at 2200 kg (3000 kg for the ram-head O.8-BA) the Riva 8-Series were heavily built with their main column and foot cast as one. Fitted with a 1300 x 300 mm table with three 16 mm T-slots on 80 mm centres. Longitudinal, traverse and vertical movements were, respectively, 1000, 330 and 470 mm with 12 rates of power feed available from 10 to 500 mm/min in both directions horizontally and from 5 to 250 mm vertically Rapids were a standard fit on each axis at a rate longitudinally and across of 2000 mm/min and vertically at 1000 mm/min. All feeds passed through a positively lubricated gearbox, that included a multi-plate clutch, and were driven by a take-off from the main spindle motor. By the early 1970s this system had been abandoned and the feeds gearbox fitted with its own 2 h.p. motor. Once running, the operation of the table feeds and rapids was by a number of long handles all of which reached towards the operator and required the minimum of effort to operate.
Models U.8 and O.8
Running in specially selected, high-precision taper roller bearing, the spindle incorporated a dynamically flywheel assembly that was claimed to smooth out the drive, provide a reserve of torque for larger jobs and give a better surface finish when using large-diameter cutters. The first models (like the 6-Series models) were equipped with an I.S.A taper, later ones with the more common and useful I.S.0. 50 - though the accessory heads all retained their I.S.A. or I.S.O 40 fitting as used on the U.6 and O.6 version. 12 speeds were provided, from 25 to 1200 r.p.m., the pressure-lubricated gearbox, with hardened and ground gears, being driven by a base-mounted 3 h.p. motor on the first models and by a 4 h.p. on later, post 1960s machines. The miller had two mechanical, plunger-type oil pumps, one for the spindle gearbox and another for the feds with a third hand-operated one, located in the saddle, to distribute oil to the table and knee ways.
Although the ordinary, oil-bath-lubricated vertical heads - the standard single-swivel T.V.8 and double-swivel Universal T.U.8  - were correctly sized for the U.8 and O.8 machines -  their other fitments (the Boring Head with Auto Down-feed and the High-speed Head) were not, being the same units as offered for the smaller models. However, the M.8 Slotting Attachment was also unique to the No. 8 and had a stroke adjustable between 0 and 100 mm. As with the smaller Riva millers, the 8-Series was offered with a unit intended just for worm milling - the Fixed Head Type C.R.8. This could handle Modular gears from 0.5 to 8 and DP equivalents and was available with a special holding attachment to fit on the Universal Dividing and Spiral-milling Head. The latter was the same 130 mm centre-height unit used on 6-Series machines with its spindle revolving in roller bearings and driven in the normal way from gearing at the right-hand end of the table. It was sold complete with 2 indexing plates, an adjustable intermediate rest, two centres, a catchplate, an extension arm to carry gears for differential indexing (13 gears were supplied) and a set of ready-reckoner tables for performing divisions - with 2200 already calculated for spiral pitches..
Model O.8-BA
Identical to the U.8 and O.8 in respect of column, knee, table, feed rates and horizontal drive motor, the O.8-BA was fitted with a special self-contained, oil-bath geared overarm that converted the machine into a form of ram miller. The arm could be moved so that the spindle line was as far away as 650 mm from the inside surface of the column. Fitted with an ISO-40 nose and 80 mm of fine down-feed by handwheel, the spindle was held in a housing that could be swivelled in two planes. Driven by a 4 h.p. motor 12 speeds were available from a low of 25 to a high of 1200 r.p.m. selected by the juxtaposition of three levers on arms' left-hand face..

Running in specially selected, high-precision taper roller bearing the spindle incorporated a dynamically flywheel assembly that was claimed to smooth out the drive, provide a reserve of torque for larger jobs and give a better surface finish when using large-diameter cutters. The first models (like the 6-Series models) were equipped with an I.S.A taper, later ones with the more common and useful I.S.0. 50

Automatic-feed Boring Head with an I.S.O. 40 taper, 12 spindle speeds from 30 to 1500 r.p.m. and both a lever-action quick feed and a fine feed through worm-and wheel gearing and a handwheel fitted with a very large diameter micrometer dial. The spindle had a travel of 150 mm and the head could be tilted over 45° in each direction from upright. 2 rates of power down-feed were available: 0.05 and 0.1 mm per revolution

An effective and well-designed 130 mm centre height Universal Dividing and Spiral-milling Head was offered; complete with a tailstock it was driven from gearing at the right-hand end of the table with its spindle revolving in roller bearings. It was sold complete with 2 indexing plates, an adjustable intermediate rest, two centres, a catchplate, an extension arm to carry gears for differential indexing (13 gears were supplied) and a set of ready-reckoner tables for performing divisions - with 2200 already calculated for spiral pitches.

Lacking a quill feed, but containing gears finished on Gleason machinery and running in an oil bath, the T.V.8 and T.U.8 heads were driven from the horizontal spindle but arranged with step-up gearing to provide a slight increase in speed - the range running from 30 to 15000 r.p.m. While the Type T.V.8 (left) had a single swivelling end, the T.U.8 (right) had a double

Universal High-speed Head Type T.V.U. This had a lever-action quill with the spindle driven by its own 2-speed, 0.6/0.4 h.p. motor that gave, via V-belts, speeds of 500, 750, 1000, 1500, 2000 and 4000 r.p.m. The same unit was used on all Riva Milling machines

A rather special attachment, designed exclusively for rack and worm milling, was the Fixed Vertical Head. Type C.R.8 This could handle Modular gears from 0.5 to 8 and DP equivalents and was available with a special holding attachment to fit on the Universal Dividing Head.